Woody vines amplify the effects of lightning in tropical forests

Across the tropical regions of the world, forests face a myriad of challenges brought on by global change. One such challenge is the combined impact of increased lightning frequency and the prevalence of woody vines known as lianas. 

In a new study supported by the National Science Foundation, researchers have investigated the potential impacts of this phenomenon. The experts found that the “one-two punch” of lightning and lianas is causing higher mortality rates among smaller trees. This could ultimately alter the composition of tropical forests and reduce their capacity to store carbon.

Matt Kane, a program director in NSF’s Division of Environmental Biology, highlighted the importance of understanding the consequences of ecological disturbances driven by climate change. “Knowing the short- and long-term effects of lightning strikes is helping improve scientific understanding and sustainability of tropical forest ecosystems.”

Tropical forests are subject to approximately 35-67 million lightning strikes each year, with a growing trend toward more frequent strikes. Lead author Evan Gora, a scientist at the Cary Institute of Ecosystem Studies, noted that “lightning is a major cause of tree death and forest disturbance, yet it has been understudied as an agent of change.” 

Gora and his team set out to determine why certain lightning strikes cause more tree deaths than others, and found that lianas play a crucial role. Lianas are long-stemmed, woody vines that are prevalent in tropical forests. These plants compete for sunlight by climbing trees and extending into their canopies. 

The researchers discovered a positive correlation between liana density and the number of trees killed or damaged by lightning. Their research suggests that this is because lianas are highly conductive and serve as a conduit for electrical current to flow from large trees to smaller ones.

“Large trees are more likely to be struck by lightning. When lianas are in the canopy, they amplify the effects of lightning strikes, resulting in more severe damage to neighboring trees,” said Gora. He explained that “by physically connecting trees that would otherwise be separated, lianas act like jumper cables, delivering deadly electrical current to smaller understory trees that would otherwise survive a lightning strike.”

How the research was conducted

The study was conducted in a lowland forest on Barro Colorado Island, Panama, which is the only tropical forest where lightning impacts have been systematically quantified. Researchers estimate that lightning is responsible for the death of more than 16 percent of tree biomass annually on the island, including 40-50 percent of the largest trees.

To investigate the role of lianas in lightning disturbance severity, the team used a novel lightning detection system. They conducted surveys on 78 lightning strikes in areas with mapped liana presence and monitored 1,921 trees that had sustained visible lightning damage. Tree conditions were assessed within four months of the lightning strike and up to four times within the following 23 months. 

The findings of this study shed light on the complex relationships between lightning, lianas, and tropical forests, as well as the potential implications for forest ecosystems as a whole. The research is published in the journal New Phytologist.

Tropical forests face multiple threats

Tropical forests, which are some of the most biodiverse and ecologically significant ecosystems on Earth, face a variety of challenges and threats. These issues not only jeopardize the health and stability of these forests but also have global implications for climate change and biodiversity conservation. Some of the key issues faced by tropical forests include:

Deforestation

Large-scale clearing of tropical forests for agriculture, logging, infrastructure development, and mining is a major threat to these ecosystems. Deforestation results in habitat loss, fragmentation, and degradation, which can lead to a decline in biodiversity and disrupted ecosystem functioning.

Climate change

Rising temperatures, changes in precipitation patterns, and more frequent and severe weather events due to climate change pose significant challenges for tropical forests. These changes can affect forest structure, composition, and function, as well as increase the risk of wildfires, pest outbreaks, and disease.

Invasive species

Non-native species can be introduced to tropical forests intentionally or accidentally, and they can have severe ecological impacts. Invasive species can outcompete native species for resources, disrupt ecosystem processes, and even lead to the extinction of native species.

Over-exploitation 

Over-harvesting of timber, fuelwood, and non-timber forest products can lead to forest degradation and a decline in biodiversity. Unsustainable hunting and poaching can also threaten wildlife populations and disrupt ecological balance.

Pollution

Air, water, and soil pollution from industrial and agricultural activities can have detrimental effects on tropical forests. Contaminants can harm plants and animals, disrupt nutrient cycling, and affect overall forest health.

Disease and pests

Pests and diseases can cause significant damage to tropical forests, especially when exacerbated by climate change and habitat disturbance. These threats can result in the decline of specific tree species, which in turn can affect the overall structure and function of the forest ecosystem.

Land-use change

Changing land-use patterns, such as urbanization and agricultural expansion, can lead to the conversion of tropical forests into other land uses. This process contributes to habitat loss and fragmentation, as well as increased human-wildlife conflict.

To address these challenges, it is vital to implement effective conservation strategies, promote sustainable land-use practices, and raise awareness about the importance of tropical forests. This will help protect these valuable ecosystems and the numerous species that depend on them, while also mitigating the impacts of climate change and preserving vital ecosystem services for future generations.

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